This invention relates to tufting machines and more particularly to a tufting machine wherein the needles are carried by needle holders which are selectively latched to a reciprocating latch bar, the needle holders being mounted between guide plates adjustably mounted in the machine.
Tufting machines which produce carpet, basically include a large frame having a head within which a rotatable mainshaft is mounted and from which needle driving structure is supported for reciprocating a multiplicity of needles. The frame also includes a bed within which oscillating loopers or hooks are mounted for cooperating with the needles to form loops of yarn, knives being used in conjunction with the hooks to cut the loops in many tufting machines. As the tufting art has developed, there have been a substantial number of innovations to obtain unique patterning effects. One such innovation has been to shift the needles laterally in accordance with a pattern. Another innovation has been to provide each needle with a sew/no-sew capability by mounting the needles on individual needle holders which are reciprocated selectively by either being latched to or disengaged from a reciprocating latch bar, the latter being reciprocably driven continuously from mechanism driven by the rotating mainshaft. When latched to the latch bar, the needle reciprocates into cooperation with the hook to form a loop. The latching occurs by means of latch pins on pneumatic cylinders driven in accordance with a pattern. Machines of this type are known as controlled needle machines, and when each needle is individually controlled in this manner, it is known as an individual controlled needle machine.
A recent development in the tufting art is to combine the individual control needle machine concept with the shifting needle concept, and to feed the backing material intermittently. This provides a tufting machine wherein the needles may be threaded with a number of different yarns, e.g., yarns of different colors, and a needle having a yarn of a particular color may be inserted into the backing at any of a selected number of locations so that extremely precise multi-color patterns may be produced similar to the fine woven carpets produced by looms. A machine of this type is illustrated in Bardsley U. S. Pat. No. 5,653,184.
In such tufting machines, as illustrated in the aforesaid patent, the needles are individually mounted in an elongated holder, one end of which is adapted for latching to the latch bar and the other end of which mounts the needle. The needle holder is normally biased by a return spring into a non-sewing position and is driven into a sewing position during sewing against the bias of the spring by the needle drive arrangement. The needle holder includes a spring biased ratchet-like clamp arrangement which causes the yarn to be drawn from the supply when the needle holder moves from the non-sewing position to the sewing position by trapping the yarn between the clamp and a wall of the holder. When the needle holder moves back to the non-sewing position, the tension on the yarn urges the clamp away from the wall of the holder so that the yarn can pass through the clamp.
A problem that has arisen with this construction of the prior art is that the ratchet-type clamp of the needle holder is in a position whereby access to the spring for removal or replacement is difficult. In a majority of cases if these parts fail or need replacement, it has been necessary immediately to replace the entire needle holder, thereby increasing cost of replacement parts and machine down-time. The spring in the prior art is within the body of the needle holder or within an extension secured to the needle holder, the extension having a deep slot milled between two thin wall portions. Pins within the slot must be positioned so as to guide yarn and hold the ratchet-type mechanism and spring within the slot. A coil spring having two legs one of which is disposed about the pin on which the clamp is journalled and the other of which is disposed about another pin so as to bias the clamp against the yarn is disposed within the slot. The slot within the needle holder is milled so as to leave a little material at the end to permit a hole to be formed for mounting the pin about which the spring is curled.
Moreover, the needle holder on such machine is mounted for movement by means of a pair of ridged guide blocks or plates having parallel channels therein. The guide bars or plates are secured to a top and bottom surface of a needle support bar and the ridges or channels in the guide plates define therebetween positions in which respective needle holders can be mounted. A corresponding ridged pair of fixing plates are secured to a top and bottom surface of a fixing bar and can be secured in a position relative to the guide plates so that the needle holders are secured in position in a tufting machine intermediate respective ridges formed in the guide plates and fixing plates. Each of the fixing and guide plates is adjustable relative to the needle support bar and/or fixing bar in order to allow the needle holder to be adjusted to ensure accurate alignment with the drive mechanism. The drive plates and fixing plates may be modular in so far as they have a width such that each plate retains only a small number of needle holders in position in the machine.
The arrangement of the mounting blocks in the prior art is such that the needle holders cannot be removed readily from the tufting machine in a direction transverse to the direction of reciprocation, and thus in order to remove the needle holder it is presently required to penetrate the backing material, cut an opening and remove the needle holder in the vertical or reciprocation direction.
A problem arises with this existing mounting system since the correct alignment of the needle holder and the drive mechanism are dependent upon the relative positioning of at least four plates, thereby making it difficult and time consuming to achieve such correct alignment.
Additionally, thermal expansion may cause the guide plates and/or the needle holder to vary in shape or dimension. If the needle holder has a straight or dovetail cross sectional configuration as in the prior art, such expansion may result in the needle holder becoming misaligned by twisting or rotating slightly in the guide. The thermal expansion resulting in such variation may be caused by frictional heating of the guide plate and/or the fixing plate during operation.